<a href="http://haskell.org/haskellwiki/TypeCompose">TypeCompose</a> provides some classes & instances for forms of
type composition. It also includes a very simple implementation of
data-driven computation. I factored it out of a new implementation of <a href="http://haskell.org/haskellwiki/Phooey">Phooey</a>. I am very interested in comments and contributions.<br><br> - Conal<br>